1. Field of the Invention
This invention relates to a multichannel optical measuring system, more particularly to a multichannel optical measuring system for measuring the optical response of a sample illuminated by light.
2. Description of the Prior Art
In recent years fluorochromes that have been developed are being used for quantitative measurement of calcium ions, magnesium ions and the like in various types of blood cells. However, systems now in use for measuring fluorescent and transmitted light are single channel systems for making measurements relating to just one sample or for measuring the optical response obtained with an incident light beam of just one wavelength.
However, such single channel systems cannot be used when a large number of samples have to be measured in a short space of time, such as for measurements relating to floating cells in the blood such as platelets, leukocytes and lymphocytes, with the aim of measuring changes in the calcium ion or magnesium ion content of blood platelets, for example, while at the same time measuring changes in the aggregation of such cells.
To provide a conventionally configured system with multichannel fluorometry capabilities would involve the addition of as many light sources as there are sample (measurement) cuvettes to be measured, and the corresponding optical systems for condensing the light from these sources and selecting wavelengths. The only way to do this would be to use an array of conventional single channel systems, which would result in an impractically large and costly arrangement.
Then there is the fact that fluorometry involves the use of costly high-voltage mercury or xenon lamps, and each optical system needs to have a switchover unit to switch among diffraction gratings or interference filters for measuring fluorescent intensities obtained at multiple wavelengths. The ability to measure changes in a cell's fluorescent intensity while at the same time measuring the intensity of the light transmitted by the cell enables the chemical composition of the cell to be determined from the spectral absorption characteristics and the shape of the cell to be determined from the scattered light. When studying cell physiology and pharmacological effects, such data is useful by enabling the relationships among the various parameters to be ascertained.
However, measurement systems based on conventional technology make simultaneous use of two photosensors, one being a photomultiplier that is used as the fluorescent photosensor and the other being a photodiode that is used as the transmitted light photosensor. Moreover, the beam of illumination used for measurement of fluorescence and the beam of illumination used for measurement of transmitted light are both projected along the same optical path to the measurement cuvette, a configuration that is not suitable for multichannel measurements. In addition, to implement the conventional system arrangement, in which a photomultiplier is used as a photosensor to facilitate measurement of the weak fluorescence, requires a large light-receiving section disposed near the measurement cuvette. In the case of a multichannel system having multiple measurement cuvettes, such an arrangement using photomultipliers as the photosensors would again be too bulky and costly.